The basic function of a magnetic media follower device is to control the intimate contact between the magnetic head and the magnetic media, such as a photographic film or magnetic tape. To accomplish this there are two primary functional requirements. A load applying member, frequently in the form of a leaf or reed-like spring, forces the media against the surface of the head for magnetic reading or writing. The second is the ability for the device to track the edge of the media by means of a follower unit so that variations in the cut quality of the media or inaccuracies due to splicing of media do not impact the positioning of the head relative to the edge of the media.
Known follower units incorporate a multiple function ball carrier assembly which responds to variations in the edge of a media by swiveling through a small angle on the bearing balls of the plate. Such carders require sufficient clearances between adjacent surfaces of the assembly and between the bearing balls and their receptacles to allow motion of the assembly. Excessive clearances result in contamination from dust and dirt particles and wear on parts which move relative to other parts. Excessive angular travel due to the excessive clearances can result in an unstable condition that can cause damage to surrounding assemblies or critical components of the follower assembly. Furthermore in a two-head device it is critical that adequate design features be included to ensure that the different heads are correctly oriented with respect to the magnetic tracks on each edge of the media.
A consideration in designing magnetic follower devices for photo finishing equipment which are subject to extensive use and wear is that the component parts be replaceable without requiting full disassembly of the mechanical unit. In a two-head device it is desirable to have an inventory of critical parts that can be used on either side of the assembly and to minimize parts with left and right hand components.
U.S. Pat. No. 5,034,836 discloses a magnetic head suspension apparatus for use with photographic film which includes a movable support mounted for movement through an arc having a predetermined radius and a pair of magnetic head suspension assemblies each rotatably mounted on the moveable support. The suspension assemblies are biased towards each other to cause surfaces of the magnetic head assemblies to engage opposite edges of a photographic film respectively. One of the suspension assemblies is fixed and acts as a stop which locates the entire suspension apparatus relative to the position of a film, while the other side floats and moves relative to the centerline of a film. With this arrangement the fixed edge side must be precisely aligned with other components in the film path to ensure smooth transport of the film. The entire assembly is formed of symmetrical components.
U.S. Pat. No. 5,274,522 discloses a magnetic head-to-media backer device comprising a member adapted to urge a flexible magnetic media into contact with a magnetic head. The rigid frame for holding the member has a cavity and various embodiments of the cavity are described.
U.S. Pat. No. 5,285,324 discloses a magnetic reading and/or recording apparatus which includes a plurality of magnetic reading and/or recording elements to read and/or record information from/on a flexible magnetic recording material, and a flexible plate. A means for arranging the elements and the flexible plate to contact the magnetic recording material with the elements is included, the arranging means includes a pressure pad mounting block having a recess to accept the flexible plate.
U.S. Pat. No. 5,285,325 discloses a two-headed magnetic recording or playback assembly for a camera that includes two symmetrical pressure pad mounting blocks.
It is an object of this invention to provide a follower assembly designed with minimal clearances between components to prevent contamination and wear.
It is an object of this invention to provide a follower device with a ball carrier mounting plate assembly having dissimilar ends which enables the device to be correctly oriented in an apparatus.
It is an object of this invention to provide a follower device with a ball carrier mounting plate assembly in which both sides float relative to the centerline of a media being tracked.
It is an object of this invention to provide a follower device designed to rotate with a minimal angular travel without causing excessive movement and unstable conditions during tracking.
It is an object of this invention to provide a follower device designed to minimize positional inaccuracies by including interface features such as tabs, slots and notches to minimize assembly variations.